Birth monitoring system

ABSTRACT

A medical transponder, including an ultrasonic sensor that detects impinging ultrasonic waves and generates electrical signals in response thereto; an electrical connection which receives said signals; and an electromagnetic RF transmitter coupled to said electrical connection and which generates an RF signal in response to said detected waves.

RELATED APPLICATIONS

[0001] This application claims the benefit under 119(e) of the followingprovisional applications: Ser. No. 60/295,569 filed 5 Jun. 2001, Ser.No. 60/295,573, filed 5 Jun. 2001, Ser. No. 60/309,783, filed 6 Aug.2001 and Ser. No. 60/338,671, filed Dec. 11, 2001. This application isalso related to a PCT application filed on even date with thisapplication by applicant in the Israel receiving office and havingattorney docket 330/02602, the disclosure of all of these applicationsis incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to intrabody position monitoringsystems.

BACKGROUND OF THE INVENTION

[0003] The birth of a human child is a complicated and traumaticprocess, of whose mechanical and geometrical aspects, surprisinglylittle is known. In a normal birth, the cervix dilates and a fetus ispushed out from a uterus and along a birth canal (e.g., the vagina),which lies between the pubic bones. This is described in greater detail,for example, in Williams Obstetrics Cunningham, Gary et al. Appleton &Lange 20th edition, the disclosure of which is incorporated herein byreference. Due to the relatively large size of the head of the fetus,not only is the head distorted by this passage, but it must also changedirection and turn during the passage. First, however, the head mustexit the uterus through the cervix, which requires the cervix to dilatea large amount.

[0004] It is common practice to monitor the progress of birth bymeasuring the degree of cervical dilation and monitoring contractionfrequency (other parameters may be monitored as well, such as maternalheart rate). At a later stage, birth progress is estimated based on thelocation of the fetus's head. The locations along the birth canal aredefined as stations. Currently, the gold standard of measurement fordilation, head orientation, station, effacement and cervical consistencyis the human hand. However, this measurement method is not onlyunsanitary, it is also intrusive and inaccurate. Since the accuracy andmeaning of the measurements depends on the person measuring (and evenfor a same person a 1 cm error is considered normal), when shiftschange, measurements change. In addition, it is hypothesized that thecervix dilation increases momentarily during contraction, and fetus headlocation and orientation changes. These variations cannot be measuredcontinuously in a reliable manner manually, reducing the amount ofinformation available, for example, the effect of each contraction.

[0005] Various mechanical and electrical systems have been devised tomeasure cervical dilation and/or fetus head location, for example asdescribed in “Cervimetry: A Review of Methods for Measuring CervicalDilation During Labor”, Obstetrics & Gynecology Survey, Vol. 55, No. 5,2000 and U.S. Pat. Nos. 5,222,485, 6,039,701, 6,246,898, 5,935,061 and6,200,279, the disclosures of which are incorporated herein byreference. These methods include, for example, Obstetric glovesincorporating a measuring string, finger mounted angular V calipers,Cervix mounted angular V calipers, induction transmitters and receiversclamped to two sides of the cervix opposite each other, a multi-switchmembrane inserted in the uterus and pressed between the cervicalinternal os and the fetal head and magnetic filed position sensors.

[0006] A Ph.D. thesis By Robert Neal Wolfson, of September 1974,submitted to Case Western University, Department of BiomedicalEngineering and titled “An Instrument for the Continuous andQuantitative Determination of Fetal Descent by Measurement of UltrasonicTransit Time (1975)”, the disclosure of which is incorporated herein byreference, suggests using ultrasonic waves and triangulation todetermine a location of a fetus's head, using ultrasonic sensors placedinside the body to detect an ultrasonic field generated outside thebody. One potential problem with this approach is that wires arerequired to connect to the ultrasonic sensors inside the body. Providingultrasonic transmitters inside the body may not be a viable solution,due to their size. Using ultrasonic transmitter/receivers or reflectorsmay also be difficult, since they require transmission of ultrasoundthrough tissue which may suffer from noise degradation and other effects(e.g., due to the many interfaces between different materials,significant accuracy and signal to noise problems may be experienced).

SUMMARY OF THE INVENTION

[0007] An aspect of some embodiments of the invention relates to awireless transponder for intrabody medical uses, which detects anultrasonic wave and generates an electromagnetic signal indicative ofthis detected wave, for example, an RF signal. In an exemplaryembodiment of the invention, when the RF signal is detected, therelative or absolute time of arrival of the ultrasonic signs can bedetermined by measuring the relative time of arrival of the RF signal.In an exemplary embodiment of the invention, ultrasonic waves areutilized for ease of calculation of distances (e.g., relatively largedifferences in time of arrival), while the electromagnetic waves areused for ease of detection (e.g., noise level). Optionally, theelectromagnetic-waves are used for determining additional informationabout the transponder, for example, its orientation and/or fortransmission of identification information.

[0008] In an exemplary embodiment of the invention, the transponderincludes a power source, for example, a battery or a power source thatreceives collects power from an imposed field, such as an RF field or alight field. Alternatively or additionally, the ultrasonic signal maypower the transponder.

[0009] An aspect of some embodiments of the invention, relates to amethod of distinguishing between a set of implanted transponders. In anexemplary embodiment of the invention, the transponders are designed tobe activated and/or their signal detected by a single broadband antenna.However, each transponder uses a different frequency for receptionand/or transmission. Optionally, the frequencies are defined as aseries, for example, an arithmetic series. Alternatively oradditionally, the frequencies are harmonics. Alternatively oradditionally, each transducer transmits a set of frequencies, whichencode ID information.

[0010] In an exemplary embodiment of the invention, the transponders areactivated by an ultrasonic field and respond using narrow band RFfields, all of which are detected using a single RF antenna.

[0011] An aspect of some embodiments of the invention relates to atransponder for use in a body, in which a detector that detects a fieldis inserted in the body, for example, in a birth canal, and is attachedto a wire at the end of which (e.g., outside the body) is a transmitterwhich transmits an indication of said detection. In an exemplaryembodiment of the invention, the detection is a detection of anultrasonic wave and the transmission is by electromagnetic wave. In abirth canal example, the transmitter is outside of the body, forexample, attached to a hip.

[0012] An aspect of some embodiments of the invention relates tooperating an ultrasonic transmission/RF reception system in a variety ofcomplementary modes and/or using a plurality of receivers. In anexemplary embodiment of the invention, the modes include two or more ofnarrow-band transmission of ultrasound, narrow-band reception of RF,different geometries for different receivers, setting of trigger linesand regions of interest (ROI) by receiver aiming, broadbandtransmission, pulsed and/or burst transmission and continuous wave (CW)transmission. In an exemplary embodiment of the invention, narrow bandreception provides better frequency discrimination in low signal tonoise ratio (SNR) situations. Alternatively or additionally, antennaorientation is used to detect an orientation of a transducer, usingphase differences between receivers. In some cases, orientationinformation is used even without positional information, for example, todetermine fetal head orientation. Alternatively or additionally, an ROIsetting is used to determine if a transmitter is within a desired (orout of a desired) location and for triggering more accurate detection ofsignals. In one example, a probe on a fetal head is detected when itleaves the uterus using a CW and ROI method and once detected, anarrow-band transmission method (e.g. using bursts) is used to obtainposition information and phase information to obtain orientationinformation.

[0013] An aspect of some embodiments of the invention relates to amethod of monitoring birth in which no known and fixed externalreference position is used. Instead, the progress of the birth isdetermined by comparing the positions and/or orientation of cervicalprobes to that of one or more fetal probes. Optionally, a directionaldetector is used to identify if a probe exceeds its expected locations.

[0014] There is thus provided in accordance with an exemplary embodimentof the invention, a medical transponder, comprising:

[0015] an ultrasonic sensor that detects impinging ultrasonic waves andgenerates electrical signals in response thereto;

[0016] an electrical connection which receives said signals; and

[0017] an electromagnetic RF transmitter coupled to said electricalconnection and which generates an RF signal in response to said detectedwaves. Optionally, said electrical connection comprises circuitry.Optionally, said circuitry comprises a driving circuitry. Alternativelyor additionally, said circuitry comprises a tuning circuitry.

[0018] In an exemplary embodiment of the invention, said transmitter hasan output lower than said signal.

[0019] In an exemplary embodiment of the invention, said circuitrycomprises a non-linear element which generates harmonics.

[0020] In an exemplary embodiment of the invention, said electricalconnection drives said RF transmitter with substantially no delayrelative to said ultrasonic detection.

[0021] In an exemplary embodiment of the invention, the transpondercomprises a covering adapted to protect said transponder from fluids andpressures extant in a birth canal. Optionally, said covering isdisposable.

[0022] In an exemplary embodiment of the invention, said transponder issmall enough to avoid interfering with a birth process, when implantedin a birth canal.

[0023] In an exemplary embodiment of the invention, the transpondercomprises an integral anchor adapted for attachment to cervical tissue.

[0024] Optionally, said transponder is powered solely by said detectedultrasonic waves. Alternatively, said transponder is powered by atransmitted power field.

[0025] In an exemplary embodiment of the invention, said transponder ispowered by an integral power source.

[0026] In an exemplary embodiment of the invention, said circuitrymodifies a frequency of said detected ultrasonic waves to generate afrequency for said transmitted RF waves. Optionally, said modificationcomprises a multiplication. Alternatively or additionally, saidmodification comprises a frequency shift. Alternatively or additionally,said circuitry comprises a variable element for generating differentfrequencies from a same base circuit. Alternatively or additionally,said circuitry resonates with said impinging waves to generate saidtransmitted waves. Alternatively or additionally, said circuitrycomprises a modulation circuitry that uses said impinging waves tomodulate said transmitted waves.

[0027] Alternatively or additionally, the transponder comprises at leastone additional sensor and wherein said circuitry modulates saidtransmitted wave using a signal from said sensor.

[0028] In an exemplary embodiment of the invention, the transpondercomprises a separate transmission antenna spatially displaced from saidsensor by a wire, to a distance at least 10 times a maximal dimension ofsaid sensor. Optionally, said wire is long enough to reach from a cervixto outside of a human body, through a birth canal. Optionally, saidbirth canal is a human birth canal. Alternatively or additionally, saidbirth canal is a an equine or bovine birth canal.

[0029] There is also provided in accordance with an exemplary embodimentof the invention, a method of detecting a transponder, comprising:

[0030] transmitting an ultrasonic wave to said transponder; and

[0031] detecting an electromagnetic RF wave generated by saidtransponder in response to an interaction between said transponder andsaid ultrasonic wave. Optionally, the method comprises determining atime of flight of said ultrasonic wave from a difference between a timeof arrival of said RF wave and a time of transmission of said ultrasonicwave. Optionally, the method comprises determining a location of saidtransponder by repeating said transmitting and said detecting from aplurality of transmitter locations. Optionally, said transmissions useat least two different frequencies for two different transmissions.

[0032] In an exemplary embodiment of the invention, the methodcomprises:

[0033] providing a plurality of transponders; and

[0034] distinguishing between RF waves generated by differenttransponders. Optionally, distinguishing comprises distinguishing byfrequency. Alternatively or additionally, the method comprises excitingsaid plurality of transponders using a broadband pulse.

[0035] In an exemplary embodiment of the invention, said detected RFwave has a frequency that is a small integer multiple of a frequency ofsaid ultrasonic wave. Alternatively or additionally, said detection isnear-field detection. Alternatively or additionally, detecting comprisesdetecting using a plurality of antennas; and determining phaseinformation from said detecting. Optionally, the method comprisesreconstructing an orientation of said transducer from said phaseinformation.

[0036] In an exemplary embodiment of the invention, the method comprisesinserting said transponder in a body. Optionally, the method comprisesinserting said transponder in tissue adjacent a birth canal. Optionally,the method comprises monitoring a process of birth using saidtransmission and said detection. In an exemplary embodiment of theinvention, said birth canal is a human birth canal. Alternatively, saidbirth canal is an equine or bovine birth canal.

[0037] There is also provided in accordance with an exemplary embodimentof the invention, a method of distinguishing between a plurality ofintra-body transponders, comprising:

[0038] inserting a plurality of intra-body transponders into an animalbody;

[0039] exciting at least one of said transponders using an excitationsignal having a frequency;

[0040] detecting an electromagnetic RF signal including a contributionfrom at least one transponder, in response to said excitation signal;and

[0041] identifying the transponder from a transponder frequency of saiddetected RF signal, wherein transponder frequencies of the transpondersare a function of said excitation frequency. Optionally, detectingcomprises broadband detection for a plurality of transponderssimultaneously. Alternatively or additionally, said function is amultiplication function. Alternatively or additionally, said transponderfrequencies are shifted by a fixed frequency from each other.Alternatively or additionally, exciting comprises exciting with abroadband signal that excites a plurality of transponderssimultaneously. Alternatively or additionally, exciting comprisesexciting with a narrow-band signal that selectively excites atransponder. Alternatively or additionally, exciting comprises excitingusing an ultrasonic signal.

[0042] There is also provided in accordance with an exemplary embodimentof the invention, a transponder, comprising:

[0043] a detection sensor;

[0044] an anchor for attaching said sensor to a location of a body;

[0045] at least one wire electrically coupled to said sensor; and

[0046] a transmitter, electrically coupled to said at least one wire andadapted to be placed at a distance from said sensor, which distance isat least 10 times greater than a maximum dimension of said sensor.Optionally, said detection sensor is an ultrasound sensor. Alternativelyor additionally, said transmitter comprises an electromagnetic RFtransmitter.

[0047] There is also provided in accordance with an exemplary embodimentof the invention, a method of collecting information from one or moremedical transponders, comprising:

[0048] first transmitting an excitation signal to one or more medicaltransponders;

[0049] first receiving a first response of said transponder, saidtransmitting and receiving defining an interrogation;

[0050] second transmitting a second excitation signal to saidtransponder;

[0051] second receiving a second response of said transponder; and

[0052] analyzing said responses to provide information about saidtransponder,

[0053] wherein said first transmitting and receiving and secondtransmitting and receiving use different interrogation modes.Optionally, said interrogation modes are selected from continuous wavetransmission, pulsed transmission, region of interest transmission,region of interest detection, phase detection, broad band detection andnarrow band detection. Alternatively or additionally, saidinterrogations share at least one receiving antenna. Alternatively oradditionally, said interrogations share at least one transmissionantenna. Alternatively or additionally, said interrogations use the sametransmission and reception antenna for both interrogation modes.

[0054] There is also provided in accordance with an exemplary embodimentof the invention, a method of monitoring a progress of a birth,comprising:

[0055] determining a position of at least one cervical transponderrelative to a transmitter, which transmitter has a location notregistered to fixed reference of the mother;

[0056] determining a position of at least one fetal transponder relativeto said transmitter; and

[0057] displaying a relative position of said at least one cervicaltransponder and said at least one fetal transponder. Optionally, themethod comprises determining and displaying a relative orientation ofsaid transponders.

[0058] There is also provided in accordance with an exemplary embodimentof the invention, a birth monitoring system, comprising:

[0059] an ultrasonic transmitter comprising at least one transmissionelement;

[0060] an electromagnetic RF receiver comprising at least one RFantenna;

[0061] at least two transponders adapted to attach to a cervix and whichgenerate RF signals responsive to excitation by an ultrasonic signal;

[0062] a signal distinguisher which distinguishes between RF signalsfrom different transponders; and

[0063] a controller which analyzes said RF signals to produce anindication of a progress of a birth. Optionally, said indicationcomprises a dilation of said cervix. Alternatively or additionally, saidindication comprises a station of a fetal head. Alternatively oradditionally, said indication comprises an orientation of a fetal head.Alternatively or additionally, said system is adapted to be worn by amother being monitored. Alternatively or additionally, saiddistinguisher is part of said controller.

BRIEF DESCRIPTION OF THE FIGURES

[0064] Non-limiting embodiments of the invention will be described withreference to the following description of exemplary embodiments, inconjunction with the figures. The figures are generally not shown toscale and any measurements are only meant to be exemplary and notnecessarily limiting. In the figures, identical structures, elements orparts which appear in more than one figure are preferably labeled with asame or similar number in all the figures in which they appear, inwhich:

[0065]FIG. 1 is a side schematic view of a birth canal and uteruscontaining a fetus during delivery, on which the methods and/orapparatus of some embodiments of the present invention are applicable;

[0066]FIG. 2 is a schematic block diagram of a birth monitoring systemin accordance with an exemplary embodiment of the invention;

[0067]FIG. 3A is a showing of an application of the system of FIG. 2, tothe physiology of FIG. 1, in accordance with an exemplary embodiment ofthe invention;

[0068]FIG. 3B is a detail view of the placement of transducer probesabout a cervix, in accordance with an exemplary embodiment of theinvention;

[0069]FIG. 4 is a schematic isometric showing of a single transponderprobe in accordance with an exemplary embodiment of the invention;

[0070]FIG. 5 is a schematic block diagram of a transponder probe inaccordance with an exemplary embodiment of the invention;

[0071]FIG. 6 is a schematic diagram of a mechanism for powering thetransponder of FIG. 5, in accordance with exemplary embodiments of theinvention;

[0072]FIGS. 7A-7D are schematic circuit diagrams for transponding inaccordance with an exemplary embodiment of the invention;

[0073]FIG. 8 illustrates relative bands of transmission and receptionfor a set of transducers in accordance with an exemplary embodiment ofthe invention; and

[0074]FIGS. 9A-9C show antenna and circuitry design for an RF receiverin accordance with an exemplary embodiment of the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0075]FIG. 1 shows is a side schematic view of a birth canal and uteruscontaining a fetus during normal vertex delivery, on which the methodsand/or apparatus of some embodiments of the present invention areapplied.

[0076] A supine mother 100 has a uterus 110 with a fetus 102 inside. Inthis figure, fetus 102 has its head 104 pointed forward, towards anopening 114 in a cervix 108. Once the cervix is dilated, fetus 102 willpass through a birth canal 106 and be born. Spine 116 and pelvic bone112 constrain the path, forcing the fetus to bend and twist during thebirthing (the side pelvic bone are not shown). This example is used forreason of convenience, however, various embodiments of the presentinvention may be usefully used also when the fetus has a differentpresentation than the one shown.

[0077]FIG. 2 is a schematic block diagram of a birth monitoring system200 in accordance with an exemplary embodiment of the invention. System200 comprises at least one internal transducer probe 202, adapted to beattached to the cervix and/or the fetus.

[0078] In an exemplary embodiment of the invention, transducers 202respond to an interrogation by an at least one transmitter 204, with aresponse that is detected by an at least one receiver 206. While in anexemplary embodiment of the invention, transmitter 204 is an ultrasonictransmitter and receiver 206 is an RF receiver, this is not essential inall embodiments of the invention, and in some embodiments thetransmitter and receiver are combined as single unit (e.g., sharing anantenna).

[0079] Transmitter 204 and/or receiver 206 may operate using acontinuous wave protocol or a pulsed protocol. Further, while in anexemplary embodiment of the invention, the signals are analog andpossibly with little or no modulation, in an alternative exemplaryembodiment of the invention, the signals are modulated and/or digital.Possibly, the transmission protocol is a networking protocol, such asbluetooth or IEEE 802 and its variants. Alternatively, there is noseparate transmission protocol other than transponder probes 202generating a response to signals that they detect.

[0080] Optionally, for example as described below, a separate powertransmitter 208 is provided, to power and/or charge probes 202.

[0081] Optionally, for example as described below, additional maternalprobes 210 or interfaces for such probes are provided, for example,contraction meters, oximeters and maternal and/or fetal ECG. Optionally,such probes are provided in addition or instead in internal transducerprobes 202. In an exemplary embodiment of the invention, a controller212 is provided. This controller may have several functions, for exampleone or more of:

[0082] (a) calculate relative and/or absolute locations and/ororientations of probes 202;

[0083] (b) monitor such locations and/or orientations for generation ofalerts, for example when a birth is or is not progressing as planned orexpected or if a mishap happened or seems imminent;

[0084] (c) integrating and synchronizing probe locations to previous orcurrent images and/or readings from other probes;

[0085] (d) extract signal information from the probe signals (describedbelow);

[0086] (e) storing and retrieving relevant information from an optionalstorage 216, which may include, for example, a personal history,monitoring of previous births, an expected time table, previousmeasurements and/or their analysis from a current birth, a generalbaseline and/or calibration information;

[0087] (f) handling input from one or more input interfaces 218;

[0088] (g) generate displays for an optional display 214; and/or

[0089] (h) generate output for an optional hard-copy device 215.

[0090] Optionally, a network connection 220 is provided, for example, tocommunicate with a central monitoring station (not shown), which may beuseful for example in a hospital ward. In another example, the networkconnection is used to transmit a message, for example a text or graphicdata message, to a remote location, for example to a spouse over acellular telephone connection.

[0091]FIG. 3A shows an exemplary application of the system of FIG. 2, tothe physiology of FIG. 1, in accordance with an exemplary embodiment ofthe invention. Not all elements of system 200 are shown, for clarity.

[0092] As shown two probes 202B and 202C are mounted on cervix os 108and one probe 202A is mounted on head 104 (e.g., on the scalp). Otherarrangements are possible, for example, more probes on the cervical os.

[0093] In an exemplary embodiment of the invention, transmitter 204 isan ultrasonic transmitter. Depending on the frequency used and the exactanatomy of mother 100, it may be desirable to locate transmitter 204 ina location where a clear ultrasonic path from transmitter 204 to probes202 is available, for at least part of the birth process. Optionally,transmitter 204 is moved as needed. It should be noted that pelvic bone112 is one element which may block, reflect or otherwise confuseultrasonic signals. In an exemplary embodiment of the invention,transmitter 204 transmits using a beam with a shape, for example a coneor multiple cones, outside of which, probes 202 are not expected and/orexpected not to respond. This may be used for selective excitation ofprobes and/or excitation based on location in the body. Optionally, thetransmitter is inserted into the body, for example into the oral,vaginal or rectal cavities and/or into an artificially formed opening.

[0094] In an exemplary embodiment of the invention, after the probes areattached, a desired location for transmitter 204 is determined, in whichthe signal to noise level is high and multiple paths are not found orare not too disruptive (e.g., a calibration step). This may requirerepositioning of transmitter 204. Possibly, a plurality of possiblylocations are determined during calibration and marked on the mother'sskin, for example using a marker. Transmitter 204 may be attached to afixed reference point on the mother's body (e.g., pubic bone 112),however, this is not necessary.

[0095] Receiver 206 may be located at any convenient location, withsignal to noise being a consideration in some cases. Another possibleconsideration is lack of interference with a procedure. In a wardsituation, multiple receivers may be located in a ward, to allowpatients to ambulate. Optionally, controller 212 determines whichtransponders work as a set together using an identification signal ofthe transponders or based on similar reception properties of severalsignals, for example, temporal clustering or amplitude similarity. Ingeneral, controller 212 may reject some measurements and/or applysmoothing, for example, erroneous signals or single unexpected valuedsignals.

[0096] In an exemplary embodiment of the invention, receiver 206 isintegrated into or attached to a hospital bed, for example, its frame orunder or in the mattress.

[0097] In an exemplary embodiment of the invention, receiver 206 has alocalized field of view, which may be aimed (e.g., by moving ororienting receiver 206 and/or its antenna(s)), for example, at differentparts of a patient. In one example, this localized field is used todetect when a probe has moved to a certain area (e.g., fetal head probeoutside of a uterus).

[0098] While transmitter 204 and receiver 206 are shown with wiredconnections this is not necessary. For example, one or both may bewireless. In one example, transmitter 204 is a battery poweredultrasound source that generates a periodic signal. Such a periodicsignal may be used to synchronize transmitter 204 and receiver 206.Alternatively or additionally, a wired or wireless connection is used tosynchronize transmitter 204 and receiver 206. Synchronization may beused to provide (e.g., at receiver 206 or controller 212) an absolutetime of flight measurement for the ultrasonic signals. Alternatively oradditionally, only a relative time of flight is determined. Optionally,a reference transponder is used to provide a reference time of flight.While such a reference transponder may be located anywhere in the body,in one example, it is mounted on transmitter 204 (e.g., zero or lowfixed time of flight).

[0099] In an exemplary embodiment of the invention, the delay timecaused by the transponder circuit is ignored. Alternatively oradditionally, it is corrected, e.g., at the controller, for examplebased on measurements of this delay. Alternatively or additionally, itis calibrated by checking the delay time of a transponder placed on thetransmitter.

[0100] Various location determining methods are known in the art and maybe used. For example, transmitter 204 can include three transmitters,each of which transmits an ultrasonic signal in turn to all probes.These signals may be the same and the probes need not differentiatebetween them, in some embodiments of the invention. Alternatively, theyare differentiated, for example, by length, for example to assist indifferentiation by controller 212. The time of flight at each probe isdetermined by controller 212 based on reception by receiver 206. Optimalpositioning of transmitter 204 may also be accuracy related, for exampleit may include determining locations for which an error is minimal orbelow a threshold. The functions of transmitter 204 and receiver 206 maybe reversed, for example using RF transmission and ultrasonic reception.Alternatively, fewer than three or more than three transmitters areused, for example, one, two, four or six transmitters.

[0101] In an exemplary embodiment of the invention, receiver 206includes multiple (e.g., 1, 2, 3, 4, 5, 6 or more) axial RF antennas(e.g., coils), so that a phase and/or amplitude information can bedetected and used to determine an orientation of probes 202 relative toreceiver 206. Alternatively, each probe may include two or more spacedapart transponders. For RF probes, orientation information may bedetermined in ways known in the art. In some embodiments of theinvention the position and/or orientation of receiver 206 is alsodependent on the physiology and/or other consideration similar to thoseof transmitter 204. An exemplary calculation method for determininglocation in ultrasonic probes is described in U.S. Pat. No. 5,851,188,the disclosure of which is incorporated herein by reference.

[0102] In an exemplary embodiment of the invention, orientationinformation is used to determine the degree of cervical effacementand/or the degree and/or effect of contractions. Optionally, orientationinformation and/or location information is used to measure twisting ofcervical os 108. Alternatively or additionally, orientation informationis used to determine the passage of parts of fetus 102 past canal partsthat have attached probes. Alternatively or additionally, orientationinformation is used to determine the orientation of head 104, forexample to indicate twisting and turning of the head. Optionally, probesare attached to other parts of the fetus and assist in providing anindication of the layout of the fetus as a whole or at least those partsthat are in the birth canal.

[0103] In an exemplary embodiment of the invention, the location andorientation data is collected for forming a baseline for the currentpatient or for other patients.

[0104] In an exemplary embodiment of the invention, when probe data iscollected it is used in a comparative manner, for example, compared toan expected path. Such a path can be generated, for example, based onultrasonic studies, insertion and tracking of a probe through the birthcanal, previous case studies and/or a theoretical model. Optionally, theprobe data is used to determine retrograde contractions and/orcontraction strength (for example, by correlating non-positionalmaternal probe information, movement of fetal head during contractionand/or opening of cervix 108 during contraction).

[0105] It should be noted that there are several possible initialpresentations of fetus 102. In an exemplary embodiment of the invention,the presentation is determined, for example by imaging and entered intoinput 218. Alternatively or additionally, other methods are used, forexample, using manual checking.

[0106] In an exemplary embodiment of the invention, the process of usingsystem 200 is as follows:

[0107] (a) implantation of probes on cervix and/or fetus;

[0108] (b) positioning of transmitter and/or receiver;

[0109] (c) optional calibration of system and/or (re)positioning oftransmitter and/or receiver;

[0110] (d) collection of location and/or orientation data;

[0111] (e) optional generation of alerts or other signal based on dataprocessing;

[0112] (f) optional attachment of additional probes, for example, to thefetal head when it appears;

[0113] (g) tracking birth; and

[0114] (h) removing probes during and/or after birth.

[0115] In an exemplary embodiment of the invention, system 200 showsvarious displays, for example, a 3D path, optionally overlaid on a 2D or3D model or image of the birth canal, a dynamic Partogram, optionallyshowing not only changes but also indicating points where contractionshad a significant or insignificant effect, such as retrogradecontractions. Alternatively or additionally, a display shows short termbehavior, for example cervical dilation, head station and orientationthe last 10, 30, 60 or 120 seconds (e.g., to assess the effect of asingle contraction). Alternatively or additionally, a display shows longterm behavior, for example 30 minutes. Optionally, the effect ofcontractions is removed, for example by smoothing, averaging or othermethods of artifact removal.

[0116] Optionally, various statistics, such as minimum, maximum averageand variance are shown. Alternatively or additionally, additional timeline information, for example that measured by various sensors (e.g.,maternal, fetal heart rate, oximeter and/or EMG) is provided.

[0117] In an exemplary embodiment of the invention, the display isdependent on maternal position, for example showing different referencepaths for the fetus for different positions. Alternatively oradditionally, the various alerts are dependent on the maternal position.In an exemplary embodiment of the invention, the change in maternalposition is detected by analyzing changes in the relative or absolutelocations and/or orientations of the probe or using a reference probe(e.g., on the bed). Alternatively or additionally, phase information isused to detect a simultaneous change in orientation of several probes.Alternatively or additionally, an orientation or angular accelerationsensor is used to detect changes in maternal position.

[0118] Optionally, an imager 222 (FIG. 2) or an interface to an imageris provided, for example an ultrasonic imager. In an exemplaryembodiment of the invention, a probe 202 or a different positioningprobe is provided on the imager, so that the relative location of theimage generated by the imager and the signals generated by the probes,can be reconstructed. Alternatively, fiduciary markers may be usedand/or manual analysis may be performed.

[0119]FIG. 3B is a detail view of the placement of transducer probes(shown in schematic form) about a cervix, in accordance with anexemplary embodiment of the invention.

[0120] In an exemplary embodiment of the invention, one (or more) probe202A is placed on head 102, possibly, before it shows. Typically,patients report to the hospital after there is some cervical dilation,so the head is accessible. Alternatively, this probe may be placed at alater time, when the head is accessible. In some cases, the head probeand/or cervical probes may be implanted prior to labor beginning, forexample at a pre-birth check up. This allows detecting the onset ofbirth, for example using an ambulatory system as described below.

[0121] In an exemplary embodiment of the invention, probes 202B and 202Care placed on opposite sides of cervix 108. Thus, as it dilates andcervical opening 114 widens, the probes are displaced from one anotherand the dilation may be measured as a correlation with thisdisplacement. Optionally, during a calibration step, an initial distancebetween the probes may be ascertained, relative to an existing dilationof cervix 108. Optionally, a mapping table is provided, for examplebased on initial positioning of probe, that relates probe location andcervix dilation. This table may be generated, for example, by measuringmanually and using system 200, on a group of test subjects.

[0122] Alternatively or additionally, two probes, for example probe 202Band a probe 202D may be placed on a same side of the cervix. Theseprobes may be used to determine the effacement of cervix 108 and/ortwisting thereof, when they move and reorient relative to each other.For example, when cervix 108 dilates completely (e.g., 10 cm), lines 302may indicate the extent of cervix 108. Optionally, the relativeorientation and/or location over time of probes (e.g., probes 202A,202B, 202C and/or probe 202D) are used to determine if the probes wereproperly placed. It should be noted that if unusual results aregenerated it may be indicated to check the birth process manually orusing a viewing tube scope, independent of whether the probes failed orthere is a real physiological problem. In case of probe failure, thedetached probes or new probes can be attached again and propermonitoring continued.

[0123] In an exemplary embodiment of the invention, one or more volumesof allowed and/or disallowed locations are defined for the probes. If aprobe enters a disallowed volume or leaves an allowed volume an alertmay be generated. Alternatively or additionally, these volumes are usedto define stages in birth, for example, total effacement of cervix. Thevolumes may be dependent on maternal position. Alternatively oradditionally, changes in location of probes outside volumes and/or otherparameters are used to determine that a change in maternal position hasoccurred (e.g., lying down, side). In an exemplary embodiment of theinvention, a head probe is allowed between the pelvic inlet and outlet.Alternatively or additionally, cervical probes are allowed between aplane of the pelvic inlet and a plane of ischial spines. Alternativelyor additionally, changes of orientation are used for the same purposes,for example cervical probe orientation may indicate that a fetus ispassing by or that the cervix is completely effaced.

[0124] While two probes are shown for the cervix in general, in anexemplary embodiment of the invention, more than two probes are used,for example, three or more probes around the circumference of thecervix. This may assist in preventing dilation estimation errors causedby uneven probe placement or uneven dilation of cervix.

[0125] In an exemplary embodiment of the invention, the effacementand/or dilation of cervix 108 are tracked, for example, to generate adistortion map of cervix 108. Generating such a map may also make itdesirable to use additional probes, for example, four, five, six or moreprobes in all. While this map is useful in general for studying thecervix and determining the above mapping table, anomalies as compared toother studies may indicate a fault in the cervix which might causepremature birth or danger to mother or child. This fault can then betreated immediately or at least before a future pregnancy starts orreaches a danger point.

[0126] In an exemplary embodiment of the invention, the locations andorientations are made relative to a base location, for example, that oftransmitter 204. However, this is not essential. Possibly, the cervicalprobes are used as a reference for themselves, since, at least in someparts of the birth process, they remain in a plane. In other parts ofthe birth process, it is the relative location of the head probe and thecervical probes that is important, not the absolute location.

[0127] In an exemplary embodiment of the invention, the head station isdetermined using a fixed reference, for example a probe on the outsideof the body (or near front of birth canal) or using a known, fixedlocation of the transmitter. This position may be updated, for exampleif the probe is moved and/or calibrated, for example using an image orusing manual checking. In an exemplary embodiment of the invention, thecontroller performs transformations so that the display (if any) matchesa known standard, for example that of stations and/or expected changesin head orientation.

[0128]FIG. 4 is a schematic isometric representation of a singletransponder probe 202 in accordance with an exemplary embodiment of theinvention.

[0129] Probe 202 comprises a body 404 and an attachment mechanism 402.Various attachment means may be used, for example those known in the artor such as described in the above referenced PCT filed on same date, thedisclosure of which is incorporated herein by reference. In an exemplaryembodiment of the invention, mechanism 402 comprises a bio-absorbablebarbed spike, whose body dissolves after a time period, so that the restof probe 202 detaches by itself.

[0130] In an exemplary embodiment of the invention, attachment mechanism402 attaches probe body 404 rigidly enough that there is good ultrasoniccoupling between the cervix and the probe. For example, the mechanism,(e.g., a curved wire) provides firm contact with no spaces. Optionally,a gel is used to ensure the lack of air bubbles and/or to providesuitable acoustic impedance (e.g., as a matching layer). In an exemplaryembodiment of the invention, the attachment mechanism and/or the probeshape are designed to take into account the expected passage of a fetusagainst or adjacent the probe, with the associated friction, pressureand potential danger of damage to the fetus. For example, the attachmentmeans is aligned along the path of fetal movement, the probe isstreamlined and/or a control cable, if any, is made pliable.

[0131] Alternatively or additionally, the design takes into account anexpected need for manual checking, for example being designed not tosnag against a hand which is inserted and/or designed not to include asharp barb which may snag a hand of a fetus.

[0132] While the shape shown is spherical, other shapes may be provided,for example, flattened on one side (e.g., to confirm to birth canal),cylindrical (e.g., to better fit some electronic packages) and/or oval(e.g., pill shaped). In some embodiments of the invention, a pluralityof probes 202 are strung together, for example on an elastic thread(optionally designed to tear at low stresses, to prevent fetalstrangulation), and these probes are attached around the external cervixos 108. The length of the tread may be, for example, 37 cm incircumference.

[0133] Body 404 may be formed of a bio-compatible material, such as asuitable plastic. Alternatively or additionally, body 404 is coated witha bio-compatible material. In some embodiments of the invention, thematerial selected is suitable for short (e.g., a few days) stay incontact with mucal members. Alternatively or additionally, body 404 isprovided inside a disposable covering (e.g., a salable plastic bag), forexample, to allow probe 202 itself to be reused and, possibly preventdamage by sterilization. Alternatively, body 404 and/or its coating isdesigned to permit sterilization. Alternatively, the probe is providedfor one time use.

[0134] In an exemplary embodiment of the invention, the probe has arelatively small volume, for example, less than 2, 1, 0.5, 0.25 or 0.1cubic centimeters, or any smaller or intermediate volume. This volumeincludes the volume of the attachment mechanism which protrudes into thebirth canal.

[0135] While an ultrasonic sensor may be embedded wholly in body 404, insome embodiments of the invention, the sensor includes a surfaceportion, for example, as shown a patch 410. While a small patch isshown, a sensor may cover, for example, an entire hemisphere of body404. Alternatively or additionally, patch 410 is for a different type ofsensor, for example, a maternal ECG or EMG sensor or an oximeter.Alternatively or additionally, path 410 is used to measure properties ofthe cervix itself, for example thickness (e.g., a local ultrasonictransmitter/receiver), tension and consistency (e.g., hardness). Manydifferent types of suitable sensors are known in the art for thesemeasurements and may be used. Such sensors may be useful if probe 202 isattached to a part of fetus 102. The attachment mechanism 402 may alsoinclude a sensor, for example an attachment tension sensor, which mayprovide information about the attachment status of probe 202.

[0136] Alternatively or additionally, a sensor patch may be provided onan upper hemisphere of body 404, for example a patch 406 which may serveas a contact sensor for determining passage of fetus 102 against theprobe. Alternatively or additionally, a power receiving contact ormechanism patch 408, may be provided, for example, an optical receiveror an electrical contact for contact recharging. Alternatively oradditionally, patch 408 may be a signal antenna, for example, if IRcommunication is used instead of RF communication or if body 404 isimpervious to RF radiation.

[0137] Optionally a control wire or safety tether (not shown) isattached to probe 202. This tether may be attached, for example to thehip and be used to prevent retrograde migration of the probe and/or toassist in removal thereof. In an exemplary embodiment of the invention,the attachment mechanism comprises a normally open release mechanism(e.g., a retraction spring) which is prevented from opening by arestraint (e.g., a pin). In an exemplary embodiment of the invention,pulling on the tether may activate the release mechanism (e.g.,releasing the pin), so that no manual insertion is required for removingthe probe. Alternatively or additionally, the attachment mechanism mayweaken over time, so that when labor is over the probes may be removedwith relatively little force.

[0138] In an exemplary embodiment of the invention, the control wire isattached to an antenna and/or circuitry that is outside the body, forexample on the hip. Thus, the mother is not attached by these wires to amonitoring system, but the transmitted can be in a more convenientand/or better SNR location.

[0139] In an exemplary embodiment of the invention, body 404 ismonolithic. Alternatively, it may be openable, for example for replacinga power supply.

[0140]FIG. 5 is a schematic block diagram of a transponder probe 202 inaccordance with an exemplary embodiment of the invention. In anexemplary embodiment of the invention, an ultrasonic detector 500receives an ultrasonic signal which is conveyed to an RF generator forgeneration and/or modulation of a signal. RF generator 502 may bepowered by the ultrasound signals, alternatively, an optional powersource 506 is provided. In some embodiments of the invention, a powerreceiver 508 is provided for charging or energizing power source 506,for example as described below.

[0141] The RF signal is passed to an RF antenna 504 for transmission,alternatively, other transmission methods may be used, for example,ultrasonic and IR.

[0142] Optionally, one or more additional sensors 510 are provided,whose input optionally modulates the output of RF generator 502. While asingle ultrasound detector 500 is shown, multiple detectors may beprovided, for example, to assist in orientation determination of probe202. The two detectors may share a single RF generator and antennaand/or other associated circuitry.

[0143] Optionally, probe 202 is designed (e.g., suitable power supply)to remain on head 104 even after birth, for example being used forwireless monitoring of the fetus's location, vital signs and/or for IDpurposes.

[0144]FIG. 6 is a schematic diagram of a mechanism for powering thetransponder of FIG. 5, in accordance with exemplary embodiments of theinvention.

[0145] In an exemplary embodiment of the invention, a radiation field606, for example, RF, light, ultrasound or low frequency magnetic fieldis received by an antenna 604 (or a photocell, or otherwise depending ontype of field). Suitable circuitry (not shown) may be added, as neededand as known in the art, for example. The output signal is optionallyrectified by a circuitry 602 and provided to charge a powersource/storage 506, for example a capacitor. Optionally, circuitry 602also increases the signal voltage, for example using a transformer or aDC-DC converter.

[0146] In an exemplary embodiment of the invention, radiation field 606is intermittent, for example providing a charge when it can be provided(e.g., using a flash lamp). Alternatively or additionally, field 606 isprovided before or during generation of an RF signal by probe 202, formomentarily powering of probe 202. In some cases, no power storagecomponent is actually required. Alternatively, field 606 is continuous.

[0147] While separate power and signal detectors are shown, in someembodiments of the invention, two or more of the detector, the powerreceiver and the transmission antenna are shared. In one example, apiezoelectric crystal or other material is used both for transmitting RFand for receiving ultrasound. In another example, a same RF antenna isused for transmitting RF and for receiving RF power.

[0148]FIGS. 7A-7D are schematic circuit diagrams for transponding inaccordance with an exemplary embodiment of the invention. In operation,when probe 202 detects a pulsed ultrasonic signal from transmitter 204(or continuously, for a CW system), it generates an RF signal. In someembodiments, the received power of the ultrasonic signal is used togenerate the RF signal. Alternatively, the received signal may beamplified, the output signal is amplified and/or the generation if thesignal includes amplification. In one example, a scanning ultrasonicimaging beam can be used to set off a probe. As noted above, the imagermay be coupled to system 200, optionally also including a positionsensor to correlate positions and directions of gaze.

[0149] In some embodiments of the invention, the detected ultrasonicsignal is used to directly generate an RF signal, for example of a sameor similar magnitude. In others, it may be used to modulate a carrierwave or trigger the generation of an RF signal of an unrelatedfrequency.

[0150] As noted above, in some embodiments of the invention, it isdesirable to distinguish between probes, while this may be done bylimiting the reception bandwidth of each ultrasonic receiver, forexample, by sensor design or using a filter, in other embodiments of theinvention, distinguishing is provided by using a different carrierfrequency, modulation and/or transmission frequency for each probe. Inan exemplary embodiment of the invention, the probes are designed togenerate a frequency F+nΔf, with different probes providing differentvalues of n. In another embodiment, the frequency relationship is nF,where F is a base frequency. Frequency F maybe for example, fixed or itmay depend on the ultrasonic excitation frequency.

[0151] It should be appreciated that multiple base frequencies may beused for various reasons, for example if multiple transmitters are used.The frequencies may be odd or prime multiples, so that that can bebetter distinguished at reception (e.g., if transponders doublefrequencies).

[0152]FIG. 7A shows a simplest circuit, where a coupling capacitor C₁ isconnected to a resonance circuit composed of C₂ and L. This circuit istuned to a preferred frequency F+nΔf, optionally taking into account theelectrical properties of the rest of the probe (e.g., the capacitance ofa piezo-electric detector). Optionally, n is set by varying the value ofC₁. Optionally, C₁ may be varied by a screw, or modulated in real-time,for example, by sensor 510. Alternatively or additionally, the values ofL or C₂ are varied.

[0153] Also shown in this circuit is a simple implementation of anultrasound received, using a PZT crystal (or other suitable detector) aspart of the circuit. In this example, the detected ultrasonic wavepowers the RF transmission directly. As known in the art, the geometryof the detector may affect its sensitivity to various frequencies.

[0154]FIG. 7B shows a circuit where two diodes D₁ and D₂ are used todouble a base frequency f₁ (e.g., detected ultrasound frequency or onegenerated by a crystal). C₁ and L form a resonance circuit that is tunedto the desired output frequency. C₁ may be tuned, for example asdiscussed in FIG. 7A.

[0155]FIG. 7C shows a circuit where two circuits as in FIG. 7B are usedto quadruple the frequency. Selective use of such circuits can be usedto generate various multiples (e.g., for distinguishing purposes) fordifferent probes.

[0156]FIG. 7D shows a circuit using a nonlinear element Q, such as atunnel or pin diode, to create harmonics of f₁. A resonance circuitformed by C and L are tuned to a desired output frequency.

[0157] Not shown is an option of generating a coded ID signal (e.g., 2,4, 8 bits), for example using analog means or by providing a digitalsignal. Another option is providing digital circuitry for providing anetworking protocol, such as bluetooth.

[0158] The transmission by the transponder may be, for example,directional or non-directional. In an exemplary embodiment of theinvention, three orthogonal antennas are used to provide non-directionaltransmission. One potential benefit of directional transmission is usingamplitude to estimate orientation and/or orientation change and/or forgenerating a trigger when orientation changes. Alternatively oradditionally, directional transmission may have a better SNR. Theantenna used may be, for example, a coil antenna or an integratedcircuit antenna. Optionally, the antenna is provided in the body of theprobe or printed on its outside.

[0159]FIG. 8 illustrates relative bands of transmission and receptionfor a set of transducers in accordance with an exemplary embodiment ofthe invention. Reference 802 indicates a transmission bandwidth oftransmitter 204. As noted above, the actual transmission may be ofseveral narrow bands within this range, for example, bands 808A-808C,possibly one for each transmitting element (e.g., there may be 1, 2, 3,4 or more) in transmitter 204. Alternatively, bands 808 represent alimited detection or filtering ability of individual probes, forselective activation of probes. In an exemplary embodiment of theinvention, a broad-band has a 1 Mhz center frequency with a width of 300kHz. A narrow-band has a bandwidth of 20 kHz, for example. The exactbase frequencies and widths may depend on the application and/orimplementation (e.g., Q factor of transponder transmitter), as is wellknown in the art. The base frequency may depend, for example on thedesired accuracy (for ultrasound) and/or type of noise sources. Otherexemplary frequencies are between 100 kHz and 10 mHz or between 500 kHzand 3 mHz, with band widths of between 50 kHz and 500 kHz for broad bandand between 1 kHz and 100 kHz for the narrow band.

[0160] Reference 804 shows an RF reception envelope of receiver 206. Insome embodiments of the invention, however, the actual transmissions bydifferent probes are narrow bands, for example 806A-806C, as shown. Theexact frequency value may change in some embodiments, for example,depending on the instantaneous ultrasound transmission frequency, or ifFM is used for providing sensor readings. Alternatively, AM modulationis used for providing sensor readings. The use of broadband ultrasoundmay be useful for allowing various frequencies to be generated by theprobe and/or to provide more power and/or a better signal. In anexemplary embodiment of the invention, one of the probes transmits usinga broad-band, which may be, for example, easier to detect and/or assistin distinguishing between the probes.

[0161] While shown separated, the two frequency bands 802 and 804 mayoverlap in part or completely. It should be noted that in many cases theultrasonic wave will reach different transponders at different times.Thus, the transmitted RF waves will also be temporally separated,possibly with some overlap. Optionally, this temporal situation is usedto assist in discrimination between transmissions. Optionally an extraultrasound transmitter is provided so that at least three temporallydelayed signal series are generated by the probes for all reasonablegeometric configurations of the probes, e.g., with overlapping and/ornon-delayed signals being ignored.

[0162] In an exemplary embodiment of the invention, the probes areprovided in sets, with the bandwidth of the probes being designed tospan the available range, for example to ensure distinguishing betweenthe probes. Alternatively, other separation schemes may be used, forexample, to allow additional probes to be provided at a later time.

[0163] In an exemplary embodiment of the invention, the probes aremarked, for example to indicate their frequency and/or function (e.g.,if each probe has a different sensor). Optionally, a probe includes anassociated control cable, which may also be marked, which marking of thecable may allow for easier handling of dislodged probes.

[0164] Alternatively or additionally to bandwidth separation, differentprobes may transmit at different delays, thereby allowing distinguishingbetween probes. It is noted that this method may be more suitable whenusing a small number of probes (e.g. 3, 5, 10 or intermediate values).PCT applications PCT/US95/13232 and PCT publication WO 95/27963, thedisclosure of which are incorporated herein by reference describemethods of distinguishing between RF transmissions based on variouscoding methods. These methods may be adapted to the present application,noting that if a small number of probes is used, separation may beeasier. Alternatively or additionally, each probe may transmit atmultiple frequencies, with the set of frequencies used identifying theprobe. Alternatively or additionally, various signal characteristics,for example phase are used to identify the probes. For example, thecurrent paths of a probe may depend on its orientation which may beexpected to change at a rate lower than a threshold. For example, thespeed of rotation of the fetal head is expected to be limited. If probesampling is fast enough, this probe may be detected based on itsorientation (e.g., based on phase signals) being close to a previousvalue. Optionally, a human decision may be used to assign locationand/or signals to probes, at least for calibration purposes (e.g., basedon a physician's indication which coded probed were attached where).

[0165] Alternatively or additionally, receiver 206 includes adirectional and/or localized antenna. This may be used to detect signalsfrom only a certain part of the body, possibly assisting indistinguishing between probes and/or generating a signal if a probe isoutside (or inside) of an expected zone. Alternatively or additionally,such directional antenna are used to reduce noise levels. Alternativelyor additionally, transmitter 204 is directional, so that not all probesare excited.

[0166] As noted above, the transmitters of the probes may bedirectional, alternatively or additionally to the receiver beingdirectional. In addition, it should be noted that at the frequencies anddistances described in some of the exemplary embodiments, thewavelengths dictate a near-field type of reception. Various combinationsof directional and non-directional transmission and reception methodsfor the transducers and the receiver may be provided, some of which canuse the same system, possibly requiring switching between antenna modes.Non-directional reception may require using more than one antenna.

[0167] In one exemplary mode, both transmission and detection arenon-directional. This mode may not provide amplitude or directionalinformation, but may ensure reception and/or good SNR in allorientations. In another example, the reception is directional andtransmission is not. This mode may allow various region-of-interesttriggering methods. Exemplary triggering methods are aiming a receivingantenna at a region of interest and detecting when a transponder entersthat region. This may cause, for example, an alert to a human and/orchanging of detection mode, for example to obtain position and/ororientation.

[0168] In another example, reception is non-directional and transmissionis directional. This mode may allow orientation information to begenerated (e.g., if the signals from the reception antennas areprocessed separately) and/or may improve SNR, since the transmitter canbetter focus its energy. Also, the transmitter may be simpler in someembodiments, as a simpler antenna may be used. In another example, boththe transmission and the reception are directional. This mode may beuseful for various types of triggering (e.g., based on probe orientationand/or on its position). This mode may also provide some informationregarding the orientation of the transmitter.

[0169] It should be noted that there are two types of non-directionalreception. In one, multiple antennas are linked together so that asignal can be received independent of the transmission orientation. Inanother, the signals from the different antennas can be processed, forexample to provide the relative reception at each antenna, from whichorientation information may be provided (e.g., if transmission isdirectional).

[0170] It should also be noted that there are two types of directionalantenna. One type is directional with regard to the orientation relativeto the transmission polarization. This may be implemented, for example,using a planar coil. Another type of directional antenna is a local coildetector, which detects signals mainly from a small locality (e.g.,which may be placed near an area of interest). This may be implementedfor example, using an antenna with a small effective surface area. Inanother example, a directional antenna that is sensitive to only somedirections, is used.

[0171] In an exemplary embodiment of the invention, amplitudeinformation is also collected, which may be used, for example, forestimating distances between the RF transponders and the receiver and/orestimating power of ultrasound transmission (e.g., disturbances anddistance from ultrasound transmitter). Some orientation information mayalso be gleaned.

[0172] While it may add complexity to the transponder, in someembodiments of the invention, each transmission direction may use adifferent frequency and/or be at a different delay. This may assist indistinguishing the transponder orientation.

[0173] In an exemplary embodiment of the invention, receiver 206 and/ortransmitter 204 are operated in various modes, with each mode providinginformation, and, optionally, the information provided from the variousmodes is combined, for example, to generate a more completerepresentation of the situation and/or assist in signal detection.

[0174] For example, if a CW mode may be used simply to elicit a responsefrom a transponder. The signal, being longer, may be easier to detect,possibly using coherent detection methods. Then, a more informationalmethod may be used. A pulsed mode may be useful for other detectionmethods. A narrow band method may be useful for selective excitation ofprobes (e.g., transmission in narrow band) and/or for better accuracy(in transmission or reception) and/or for better detection (e.g., usingnarrow band receivers). A chirp mode may be used for better accuracy intime of flight determinations. Phase determination (e.g., with one ormore antennas) may be used for detecting orientation, possibly using CW.An ROI method may be used to reduce noise and/or to detect entry of aprobe into a certain area (e.g., as a trigger for an alert or a triggerfor changing detection mode).

[0175]FIGS. 9A-9C show antenna and circuitry design for an RF receiverin accordance with an exemplary embodiment of the invention.

[0176] In the configuration of FIG. 9A, two spaced apart loops areshown, the radius may be, for example 40 cm. The distance between theloops can be, for example, 60 cm. In some cases, the patient is placedbetween the loops.

[0177] In FIG. 9B, the loops are substantially co-planar. This may beuseful, for example, in placing an antenna under a pillow (e.g.,embedded in a resin mat or between two sheets of fabric).

[0178]FIG. 9C shows an exemplary reception and pre-amplificationcircuit, which may be used, for example with the receiver antennas ofFIGS. 9A and 9B. Other circuits, for example as known in the art may beused as well.

[0179] Referring back to FIG. 2, in an exemplary embodiment of theinvention, system 200 is provided as a personal monitoring system, forexample, as a device worn by a patient and possibly deployed by thepatient or a caregiver. For example, controller 212 and optionallydisplay 214 (e.g., visual and/or acoustic) are worn on a belt, which mayinclude transmitter 204 and receiver 206. Controller 212 may includesoftware for guiding a patient in a calibration or testing process. Inan exemplary embodiment of the invention, display 214 shows graphicallythe progress of labor, for example using a 3D graphical model.Alternatively or additionally, system 200 is used in a hospital ward,with receivers provided where the patient is expected to ambulate. Thesereceivers may be for detecting signals from probes 202 or from system200, in which case, the use of a standardized wireless communicationsystem in the whole hospital may be desirable. This set up, for exampleallows patients to ambulate, with an alert generated at a nurses stationand/or by the device, when labor reaches a certain stage. The exactconditions for various alerts may be set, for example, at a nurse'sstation. A plurality of receivers may be installed in the ward,optionally, each such receiver generates a signal received by a receiver(possibly receiver 206) worn by the patient, so the patient can know sheis in range.

[0180] In an exemplary embodiment of the invention, the device includesa link to a medical pump, for example, to automatically (or manually,for example via the nurse's station) control the provision ofmedication, for example, labor inducing or labor stopping medication.Alternatively or additionally, the device is integrated or linked withother wireless monitoring systems, for example, ECG and labor monitoringsystems. The integration may comprise, for example, sharing of awireless link or of a power supply.

[0181] In an exemplary embodiment of the invention, the probes areinserted by a patient. In one example, a shaped balloon or cap that fitsover the cervix is provided. Weakly attached to this balloon or cap areadhesive probes. The patient inserts the cap and waits for the adhesiveto attach. For example, the adhesive may be coated with a layer thatdissolves after a minute, to allow time for insertion. A personal cervixapplicator, designed for bringing an applicator to the lips of thecervix and which may be used for probes (e.g., with proper modificationto hold probes) is shown, for example in U.S. Pat. No. 6,352,513, thedisclosure of which is incorporated herein by reference.

[0182] In an exemplary embodiment of the invention, the system is usedfor pre-term births and monitoring thereof. For example, probes may beattached to a cervix of a mother before a due date. The mother may weara system, as described above. Alternatively or additionally, the mothermay periodically be attached (or go near) a system as described in FIG.2. Such a system may be provided, for example, in a caregiver's office,at home or in a hospital or other clinic. Optionally, the mother wears astorage device that stores information, for later upload, for example,using methods well known in the art.

[0183] While the above has focused on normal birth, it should beappreciated these methods and apparatus may be used for other types ofbirth as well. For example, in the birth of twins, probes may beattached to the two twins in parallel or in series. Possibly, thecervical probes are left in place. Alternatively they may be reattachedor replaced. In another example, probes may be attached to a leg and/ora buttocks of a fetus with a rear presentation. Alternatively oradditionally, the probes may be used during an assisted birth (e.g.,manual, vacuum, forceps), for example, to assess the effect of theassistance. The positioning of the probes may then vary over a normalvertex birth, so as to not interfere with the various assistancemethods.

[0184] While the above description has focused on human birthing, it canalso be applied to animal birthing, for example horses and cows.

[0185] The above application has focused on applications in the birthcanal in which there are various specific problems of pressure,environment, movement, interference and communication. However, thepresented systems and methods may be used for other intra-bodyapplications, for example those in which other position sensors areused, for example one or more of:

[0186] (a) Tracking, for example of catheter, endoscope, biopsy needles,stereo tactic probes, ophthalmic probes, prostate probes, amniocentesisneedles and/or invasive tools, for example in human or other animalblood vessels or lumens, for example with transponders at the tip oralong the catheter. These may be used to guide procedures (e.g.,trans-myocardial revascularization, eye surgery) or make measurements,for example of cardiac contractility

[0187] (b) Tracking and detecting of wireless devices, for example apill swallowed for imaging a GI tract and implanted drug deliverydevices of various kinds. This tracking may be used, for example, toassess progress and/or to generate alerts if the device wanders into adanger zone.

[0188] Alternatively or additionally, external medical application canbe provided, for example, assessment of joint motion, for example usingimplanted or external probes.

[0189] As can be appreciated, depending on the type of configuration andmode, the information provided about a transponder can be 1, 2, 3, 4, 5,or 6 dimensional information, selected from positional and/ororientation information.

[0190] It will be appreciated that the above described methods anddevices of transponder excitation and reception and birth monitoring maybe varied in many ways, including, changing the order of steps and theexact materials and circuits used for the devices. In addition, amultiplicity of various features, both of methods and of devices havebeen described. It should be appreciated that different features may becombined in different ways. In particular, not all the features shownabove in a particular embodiment are necessary in every similarexemplary embodiment of the invention. Further, combinations of theabove features, from different described embodiments are also consideredto be within the scope of some exemplary embodiments of the invention.In addition, some of the features of the invention described herein maybe adapted for use with prior art devices, in accordance with otherexemplary embodiments of the invention. The particular geometric formsused to illustrate the invention should not be considered as necessarilylimiting the invention in its broadest aspect to only those forms, forexample, where a spherical probe is shown, in other embodiments an ovalprobe may be used. The methods and/or controller may be implemented invarious ways, for example using dedicated hardware, software orfirmware. The scope of the invention includes devices programmed anddesigns to carry out the methods and methods performed using thedevices.

[0191] Also within the scope of the invention are kits which includesets of transducers, optionally color-coded and optionally atransmitter, a receivers and/or one or more disposable coverings.Measurements are provided to serve only as exemplary measurements forparticular cases, the exact measurements applied will vary depending onthe application. When used in the following claims, the terms“comprises”, “comprising”, “includes”, “including” or the like means“including but not limited to”.

[0192] It will be appreciated by a person skilled in the art that thepresent invention is not limited by what has thus far been described.Rather, the scope of the present invention is limited only by thefollowing claims.

1. A medical transponder, comprising: an ultrasonic sensor that detectsimpinging ultrasonic waves and generates electrical signals in responsethereto; an electrical connection which receives said signals; and anelectromagnetic RF transmitter coupled to said electrical connection andwhich generates an RF signal in response to said detected waves.
 2. Atransponder according to claim 1, wherein said electrical connectioncomprises circuitry.
 3. A transponder according to claim 2, wherein saidcircuitry comprises a driving circuitry.
 4. A transponder according toclaim 2, wherein said circuitry comprises a tuning circuitry.
 5. Atransponder according to claim 1, wherein said transmitter has an outputlower than said signal.
 6. A transponder according to claim 2, whereinsaid circuitry comprises a non-linear element which generates harmonics.7. A transponder according to claim 1, wherein said electricalconnection drives said RF transmitter with substantially no delayrelative to said ultrasonic detection.
 8. A transponder according toclaim 1, comprising a covering adapted to protect said transponder fromfluids and pressures extant in a birth canal.
 9. A transponder accordingto claim 8, wherein said covering is disposable.
 10. A transponderaccording to claim 1, wherein said transponder is small enough to avoidinterfering with a birth process, when implanted in a birth canal.
 11. Atransponder according to claim 1, comprising an integral anchor adaptedfor attachment to cervical tissue.
 12. A transponder according to claim1, wherein said transponder is powered solely by said detectedultrasonic waves.
 13. A transponder according to claim 1, wherein saidtransponder is powered by a transmitted power field.
 14. A transponderaccording to claim 1, wherein said transponder is powered by an integralpower source.
 15. A transponder according to claim 2, wherein saidcircuitry modifies a frequency of said detected ultrasonic waves togenerate a frequency for said transmitted RF waves.
 16. A transponderaccording to claim 15, wherein said modification comprises amultiplication.
 17. A transponder according to claim 15, wherein saidmodification comprises a frequency shift.
 18. A transponder according toclaim 15, wherein said circuitry comprises a variable element forgenerating different frequencies from a same base circuit.
 19. Atransponder according to claim 15, wherein said circuitry resonates withsaid impinging waves to generate said transmitted waves.
 20. Atransponder according to claim 15, wherein said circuitry comprises amodulation circuitry that uses said impinging waves to modulate saidtransmitted waves.
 21. A transponder according to claim 15, comprisingat least one additional sensor and wherein said circuitry modulates saidtransmitted wave using a signal from said sensor.
 22. A transponderaccording to claim 1, wherein said transponder comprises a separatetransmission antenna spatially displaced from said sensor by a wire, toa distance at least 10 times a maximal dimension of said sensor.
 23. Atransponder according to claim 22, wherein said wire is long enough toreach from a cervix to outside of a human body, through a birth canal.24. A transponder according to claim 23, wherein said birth canal is ahuman birth canal.
 25. A transponder according to claim 23, wherein saidbirth canal is a an equine or bovine birth canal.
 26. A method ofdetecting a transponder, comprising: transmitting an ultrasonic wave tosaid transponder; and detecting an electromagnetic RF wave generated bysaid transponder in response to an interaction between said transponderand said ultrasonic wave.
 27. A method according to claim 26, comprisingdetermining a time of flight of said ultrasonic wave from a differencebetween a time of arrival of said RF wave and a time of transmission ofsaid ultrasonic wave.
 28. A method according to claim 27, comprisingdetermining a location of said transponder by repeating saidtransmitting and said detecting from a plurality of transmitterlocations.
 29. A method according to claim 28, wherein saidtransmissions use at least two different frequencies for two differenttransmissions.
 30. A method according to claim 26, comprising: providinga plurality of transponders; and distinguishing between RF wavesgenerated by different transponders.
 31. A method according to claim 30,wherein distinguishing comprises distinguishing by frequency.
 32. Amethod according to claim 30, comprising exciting said plurality oftransponders using a broadband pulse.
 33. A method according to claim26, wherein said detected RF wave has a frequency that is a smallinteger multiple of a frequency of said ultrasonic wave.
 34. A methodaccording to claim 26, wherein said detection is near-field detection.35. A method according to claim 26, wherein detecting comprisesdetecting using a plurality of antennas; and determining phaseinformation from said detecting.
 36. A method according to claim 35,comprising reconstructing an orientation of said transducer from saidphase information.
 37. A method according to claim 26, comprisinginserting said transponder in a body.
 38. A method according to claim37, comprising inserting said transponder in tissue adjacent a birthcanal.
 39. A method according to claim 38, comprising monitoring aprocess of birth using said transmission and said detection.
 40. Amethod according to claim 38, wherein said birth canal is a human birthcanal.
 41. A method according to claim 38, wherein said birth canal isan equine or bovine birth canal.
 42. A method of distinguishing betweena plurality of intra-body transponders, comprising: inserting aplurality of intra-body transponders into an animal body; exciting atleast one of said transponders using an excitation signal having afrequency; detecting an electromagnetic RF signal including acontribution from at least one transponder, in response to saidexcitation signal; and identifying the transponder from a transponderfrequency of said detected RF signal, wherein transponder frequencies ofthe transponders are a function of said excitation frequency.
 43. Amethod according to claim 42, wherein detecting comprises broadbanddetection for a plurality of transponders simultaneously.
 44. A methodaccording to claim 42, wherein said function is a multiplicationfunction.
 45. A method according to claim 42, wherein said transponderfrequencies are shifted by a fixed frequency from each other.
 46. Amethod according to claim 42, wherein exciting comprises exciting with abroadband signal that excites a plurality of transponderssimultaneously.
 47. A method according to claim 42, wherein excitingcomprises exciting with a narrow-band signal that selectively excites atransponder.
 48. A method according to claim 42, wherein excitingcomprises exciting using an ultrasonic signal.
 49. A transponder,comprising: a detection sensor; an anchor for attaching said sensor to alocation of a body; at least one wire electrically coupled to saidsensor; and a transmitter, electrically coupled to said at least onewire and adapted to be placed at a distance from said sensor, whichdistance is at least 10 times greater than a maximum dimension of saidsensor.
 50. A transponder according to claim 49, wherein said detectionsensor is an ultrasound sensor.
 51. A transponder according to claim 49,wherein said transmitter comprises an electromagnetic RF transmitter.52. A method of collecting information from one or more medicaltransponders, comprising: first transmitting an excitation signal to oneor more medical transponders; first receiving a first response of saidtransponder, said transmitting and receiving defining an interrogation;second transmitting a second excitation signal to said transponder;second receiving a second response of said transponder; and analyzingsaid responses to provide information about said transponder, whereinsaid first transmitting and receiving and second transmitting andreceiving use different interrogation modes.
 53. A method according toclaim 52, wherein said interrogation modes are selected from continuouswave transmission, pulsed transmission, region of interest transmission,region of interest detection, phase detection, broad band detection andnarrow band detection.
 54. A method according to claim 52, wherein saidinterrogations share at least one receiving antenna.
 55. A methodaccording to claim 52, wherein said interrogations share at least onetransmission antenna.
 56. A method according to claim 52, wherein saidinterrogations use the same transmission and reception antenna for bothinterrogation modes.
 57. A method of monitoring a progress of a birth,comprising: determining a position of at least one cervical transponderrelative to a transmitter, which transmitter has a location notregistered to fixed reference of the mother; determining a position ofat least one fetal transponder relative to said transmitter; anddisplaying a relative position of said at least one cervical transponderand said at least one fetal transponder.
 58. A method according to claim57, comprising determining and displaying a relative orientation of saidtransponders.
 59. A birth monitoring system, comprising: an ultrasonictransmitter comprising at least one transmission element; anelectromagnetic RF receiver comprising at least one RF antenna; at leasttwo transponders adapted to attach to a cervix and which generate RFsignals responsive to excitation by an ultrasonic signal; a signaldistinguisher which distinguishes between RF signals from differenttransponders; and a controller which analyzes said RF signals to producean indication of a progress of a birth.
 60. A system according to claim59, wherein said indication comprises a dilation of said cervix.
 61. Asystem according to claim 59, wherein said indication comprises astation of a fetal head.
 62. A system according to claim 59, whereinsaid indication comprises an orientation of a fetal head.
 63. A systemaccording to claim 59, wherein said system is adapted to be worn by amother being monitored.
 64. A system according to claim 59, wherein saiddistinguisher is part of said controller.